151. Long-term spatial and temporal trends in frost indices in Kansas, USA.

• Authors:
  • Harrington, J. Jr.
  • Hutchinson, S.
  • Knapp, M.
  • Gowda, P. H.
  • Perumal, S.
  • Anandhi, A.
  • Murray, L.
  • Kirkham, M. B.
  • Rice, C. W.
• Source: Climatic Change
• Volume: 120
• Issue: 1-2
• Year: 2013
• Summary: Frost indices such as number of frost days (nFDs), number of frost-free days (nFFDs), last spring freeze (LSF), first fall freeze (FFF), and growing-season length (GSL) were calculated using daily minimum air temperature (Tmin) from 23 centennial weather stations across Kansas during four time periods (through 1919, 1920-1949, 1950-1979, and 1980-2009). A frost day is defined as a day with Tmin<0°C. The long - and short-term trends in frost indices were analyzed at monthly, seasonal, and annual timescales. Probability of occurrence of the indices was analyzed at 5%, 25%, 50%, 75%, and 95%. Results indicated a general increase in Tmin from 1900 through 2009 causing a decrease in nFDs. LSF and FFF occurred earlier and later than normal in the year, respectively, thereby resulting in an increase in GSL. In general, northwest Kansas recorded the greatest nFD and lowest Tmin, whereas southeast Kansas had the lowest nFD and highest Tmin; however, the magnitude of the trends in these indices varied with location, time period, and time scales. Based on the long-term records in most stations, LSF occurred earlier by 0.1-1.9 days/decade, FFF occurred later by 0.2-0.9 day/decade, and GSL was longer by 0.1-2.5 day/decade. At the 50% probability level, Independence in the south-eastern part of Kansas had the earliest LSF (6 April), latest FFF (29 October) and longest GSL (207 days). Oberlin (north-western Kansas) recorded the shortest GSL (156 days) and earliest FFF (7 October) had the latest LSF (2 May) at the 50% probability level. A positive correlation was observed for combinations of indices (LSF and GSL) and elevation, whereas a negative correlation was found between FFF and elevation.

152. Unraveling the long-term stabilization mechanisms of organic materials in soils by physical fractionation and NMR spectroscopy.

• Authors:
  • Fernandez, J. M.
  • Ciavatta, C.
  • Baldoni, G.
  • Marzadori, C.
  • Simpson, A. J.
  • Courtier-Murias, D.
  • Lopez-de-Sa, E. G.
  • Plaza, C.
• Source: Agriculture, Ecosystems & Environment
• Volume: 171
• Year: 2013
• Summary: The fundamental mechanisms whereby organic inputs stabilize in soil are poorly resolved, which limits our current capacity to predict the dynamics of soil organic matter (OM) turnover and its influence on soil quality and functioning. Here we fractionated soil OM from long-term experimental field plots either unamended or amended with two organic materials of different quality (i.e., solid cattle manure and crop residues) for 44 years into five measurable and meaningful pools directly related to conceptual preservation mechanisms: dissolved OM, mineral-free particulate OM located outside aggregates (unprotected from decomposition), OM occluded within both macroaggregates and microaggregates (weakly and strongly protected by physical mechanisms, respectively), and OM intimately associated with soil mineral particles (protected by chemical mechanisms). Compared to the unamended soil, the application of cattle manure and crop residues increased total organic C content by 35 and 10%, respectively. Most of these increases (up to 60 and 72% for cattle manure and crop residues, respectively) were explained by the mineral-associated OM pool, followed by the intra-microaggregate OM fraction. In general, the distribution and dynamics of N content paralleled those of C content. As determined by a range of modern nuclear magnetic resonance (NMR) techniques, including 13C cross polarization magic angle spinning (MAS), 1H high resolution (HR)-MAS, and 1H- 13C heteronuclear single quantum coherence HR-MAS NMR, the mineral-associated OM fraction was found to be predominately of microbial origin, unlike free and intra-aggregate OM pools, which were dominated by plant structures at different stages of decomposition. As a whole, our results indicate that the main mechanism by which organic inputs are stabilized and OM accrues in soils is not the physical and chemical protection of undecayed or partially degraded organic structures, but the adsorption on mineral surfaces of microbial biomass and microbial by-products resulting from microbial growth, transformation, and degradation processes. It is possible that organic amendments increase more than previously thought the microbial populations of the soil, which live, thrive, and die in close association with the mineral surfaces. This mechanism appears to be enhanced with the addition of stable organic materials.

153. Closing the yield gap could reduce projected greenhouse gas emissions: a case study of maize production in China.

• Authors:
  • Chen, X. P.
  • Zhang, F. S.
  • Li, S. Q.
  • Zhang, Q.
  • Yang, Z. P.
  • Wu, L.
  • Meng, Q. F.
  • Wang, G. L.
  • Yue, S. C.
  • Cui, Z. L.
• Source: Global Change Biology
• Volume: 19
• Issue: 8
• Year: 2013
• Summary: Although the goal of doubling food demand while simultaneously reducing agricultural environmental damage has become widely accepted, the dominant agricultural paradigm still considers high yields and reduced greenhouse gas (GHG) intensity to be in conflict with one another. Here, we achieved an increase in maize yield of 70% in on-farm experiments by closing the yield gap and evaluated the trade-off between grain yield, nitrogen (N) fertilizer use, and GHG emissions. Based on two groups of N application experiments in six locations for 16 on-farm site-years, an integrated soil-crop system (HY) approach achieved 93% of the yield potential and averaged 14.8 Mg ha -1 maize grain yield at 15.5% moisture. This is 70% higher than current crop (CC) management. More importantly, the optimal N rate for the HY system was 250 kg N ha -1, which is only 38% more N fertilizer input than that applied in the CC system. Both the N 2O emission intensity and GHG intensity increased exponentially as the N application rate increased, and the response curve for the CC system was always higher than that for the HY system. Although the N application rate increased by 38%, N 2O emission intensity and the GHG intensity of the HY system were reduced by 12% and 19%, respectively. These on-farm observations indicate that closing the yield gap alongside efficient N management should therefore be prominent among a portfolio of strategies to meet food demand while reducing GHG intensity at the same time.

154. Valuing the carbon sequestration potential for European agriculture

• Authors:
  • De Nocker, L.
  • Aertsens, J.
  • Gobin, A.
• Source: Land Use Policy
• Volume: 31
• Year: 2013
• Summary: Purpose: This paper aims at indicating the potential of agricultural measures in sequestering carbon as an option for climate change mitigation. The related value for society is estimated. Principle results: Agricultural practices like agroforestry, introducing hedges, low and no tillage and cover crops have an important potential to increase carbon sequestration. The total technical potential in the EU-27 is estimated to be 1566 million tonnes CO2-equivalent per year. This corresponds to 37% of all CO2-equivalent emissions in the EU in 2007. The introduction of agroforestry is the measure with the highest potential, i.e. 90% of the total potential of the measures studied. Taking account only of the value for climate change mitigation, the introduction of agroforestry is estimated to have a value of 282 euro/ha in 2012 that will gradually increase to 1007 euro/ha in 2030. Major conclusions: This implies that there is a huge potential which represents an important value for society in general and for the agricultural sector in specific. At the European level, only in the last few years policy makers have recognized the important benefits of agroforestry. In their rural development programmes some European countries now support farmers to introduce agroforestry. But still the current level of support is only a small fraction of the societal value of agroforestry. If this value would be fully recognized by internalizing the positive externality, we expect that agroforestry will be introduced to a very large extent in the next decades, in Europe and the rest of the world, and this will importantly change the rural landscapes. (C) 2012 Elsevier Ltd. All rights reserved.

155. Uncertainty in simulating wheat yields under climate change

• Authors:
  • Priesack, E.
  • Palosuo, T.
  • Osborne, T. M.
  • Olesen, J. E.
  • O'Leary, G.
  • Nendel, C.
  • Kumar, S. Naresh
  • Mueller, C.
  • Kersebaum, K. C.
  • Izaurralde, R. C.
  • Ingwersen, J.
  • Hunt, L. A.
  • Hooker, J.
  • Heng, L.
  • Grant, R.
  • Goldberg, R.
  • Gayler, S.
  • Doltra, J.
  • Challinor, A. J.
  • Biernath, C.
  • Bertuzzi, P.
  • Angulo, C.
  • Aggarwal, P. K.
  • Martre, P.
  • Basso, B.
  • Brisson, N.
  • Cammarano, D.
  • Rotter, R. P.
  • Thorburn, P. J.
  • Boote, K. J.
  • Ruane, A. C.
  • Hatfield, J. L.
  • Jones, J. W.
  • Rosenzweig, C.
  • Ewert, F.
  • Asseng, S.
  • Ripoche, D.
  • Semenov, M. A.
  • Shcherbak, I.
  • Steduto, P.
  • Stoeckle, C.
  • Stratonovitch, P.
  • Streck, T.
  • Supit, I.
  • Tao, F.
  • Travasso, M.
  • Waha, K.
  • Wallach, D.
  • White, J. W.
  • Williams, J. R.
  • Wolf, J.
• Source: Nature Climate Change
• Volume: 3
• Issue: 9
• Year: 2013
• Summary: Projections of climate change impacts on crop yields are inherently uncertain(1). Uncertainty is often quantified when projecting future greenhouse gas emissions and their influence on climate(2). However, multi-model uncertainty analysis of crop responses to climate change is rare because systematic and objective comparisons among process-based crop simulation models(1,3) are difficult(4). Here we present the largest standardized model intercomparison for climate change impacts so far. We found that individual crop models are able to simulate measured wheat grain yields accurately under a range of environments, particularly if the input information is sufficient. However, simulated climate change impacts vary across models owing to differences in model structures and parameter values. A greater proportion of the uncertainty in climate change impact projections was due to variations among crop models than to variations among downscaled general circulation models. Uncertainties in simulated impacts increased with CO2 concentrations and associated warming. These impact uncertainties can be reduced by improving temperature and CO2 relationships in models and better quantified through use of multi-model ensembles. Less uncertainty in describing how climate change may affect agricultural productivity will aid adaptation strategy development and policy making.

156. Carbon and greenhouse gas mitigation through soil carbon sequestration potential of adaptive agriculture and agroforestry systems

• Authors:
  • Mandi, S. S.
  • Ali, T.
  • Bangroo, S. A.
  • Najar, G. R.
  • Sofi, J. A.
• Source: Range Management and Agroforestry
• Volume: 34
• Issue: 1
• Year: 2013
• Summary: Agriculture together with agro-forestry systems are perceived as a source of significant greenhouse gas (GHG) emissions, with concomitant potentials for mitigation. It is among the economic sectors having the largest GHG mitigation potential. Conversion to invigorating land uses and implementation of recommended management practices (RMP) can enhance soil organic carbon (SOC). The adoption of these alternatives is likely to have considerable benefits for some cropping systems under moderate climate change. The C sequestration potential in soils of terrestrial ecosystems is 3x10(9) tonnes C/year or 0.05% reduction of atmospheric CO2 at the rate of 1 Mg/ha/year by improving C pool by the end of the year 2099. The role of forest and grasslands as a sink for atmospheric CO2 is the subject of active debate. The carbon stock for the period 2006-2030 is projected to increase from 8.79x10(9) tonnes C to 9.75x10(9) tonnes C with forest cover becoming more or less stable, and new forest carbon accretions coming from the current initiatives of afforestation and reforestation programme. With the knowledge and information that is now emerging, the role of agro-forest and plantations in mitigation is becoming more and more important. Over the past decades, national policies of India aimed at conservation and sustainable management of forests have transformed India's forests into a net sink of CO2. Not all improved management practices are suitable to all soils and ecological conditions. Dealing with many barriers to effective adaptation will require a comprehensive and dynamic policy approach covering a range of scales and issues. A crucial component of this approach is the implementation of adaptation assessment frame works that are relevant, robust and easily operated by all stakeholders, practitioners, policymakers and scientists.

157. Quantitative Assessment of Soil Health Under Different Planting Patterns and Soil Types

• Authors:
  • Zhou, D.
  • Wang, J.
  • Chen, Z.. L.
  • Bi, C. J.
• Source: Pedosphere
• Volume: 23
• Issue: 2
• Year: 2013
• Summary: Soil health assessment is an important step toward understanding the potential effects of agricultural practices on crop yield, quality and human health. The objectives of this study were to select a minimum data set for soil health evaluation from the physical, chemical and biological properties and environmental pollution characteristics of agricultural soil and to develop a soil health diagnosis model for determining the soil health status under different planting patterns and soil types in Chongming Island of Shanghai, China. The results showed that the majority of the farmland soils in Chongming Island were in poor soil health condition, accounting for 48.9% of the survey samples, followed by the medium healthy soil, accounting for 32.2% of the survey samples and mainly distributed in the central and mid-eastern regions of the island. The indicators of pH, total organic carbon, microbial biomass carbon and Cd exerted less influence on soil health, while the soil salinization and nitrate accumulation under a greenhouse cropping pattern and phosphate fertilizer shortage in the paddy field had limited the development of soil health. Dichlorodiphenyltrichloroethanes, hexachlorocyclohexanes and Hg contributed less to soil health index (SHI) and showed no significant difference among paddy field, greenhouse and open-air vegetable/watermelon fields. The difference of the SHI of the three soil types was significant at P = 0.05. The paddy soil had the highest SHI values, followed by the gray alluvial soil, and the coastal saline soil was in a poor soil health condition, indicating a need to plant some salt-tolerant crops to effectively improve soil quality.

158. Interactions between climate change and sugarcane management systems for improving water quality leaving farms in the Mackay Whitsunday region, Australia

• Authors:
  • Masters, B.
  • Crimp, S.
  • Thorburn, P. J.
  • Biggs, J. S.
  • Attard, S. J.
• Source: Agriculture, Ecosystems & Environment
• Volume: 180
• Year: 2013
• Summary: Nitrogen (N) lost from cropping is one of the major threats to the health of the Great Barrier Reef (GBR) in northern Australia, and there are government initiatives to change farming practices and reduce N losses from farms. Sugarcane is the dominant crop in most catchments draining into the GBR lagoon, especially those of the Mackay Whitsunday region (8400 km(2)) where sugarcane represents >99% of cropping in the catchments, and is grown with large applications of N fertiliser. As farmers and farming systems adapt to a future requiring lower environmental impact, the question arises whether climate change may influence the effectiveness of these changes, an issue rarely considered in past water quality studies. To address this question we used the APSIM farming-systems model to investigate the complex interactions between a factorial of five proposed sugarcane management systems, three soil types, three sub-regional climatic locations and four climate change projections (weak, moderate and strong, with historical climate as a 'control'). These projections, developed from general circulation models and greenhouse gas emission scenarios, estimated that median annual rainfall would be reduced by up to 19%, and maximum and minimum temperatures increased by up to 0.5 degrees C and 0.6 degrees C, respectively. Management practices, such as tillage, fallow management and N inputs, were grouped into five systems according to the perceived benefits to water quality. For example; Management System A grouped together zero tillage, soybean rotation crops, reduced N inputs and controlled traffic practices. While at the other end of the scale, System E included many severe tillage operations, bare fallows, high N inputs and conventional row spacing; practices that are still used in some areas. Importantly, this study parameterised controlled traffic systems, which is considered an important component of 'best' management in the GBR catchment, but for which water quality benefits have yet to be widely quantified. The study predicted that the improvement in farm management needed to meet water quality improvement goals will not be greatly affected by climate change. However, without any interventions, the frequency of years with very high N losses, and hence extreme ecological risk, was predicted to increase by up to 10-15%. Compared with traditional practices, improved management systems were predicted to reduce N losses by up to 66% during these years. The results support continued adoption of improved management systems to achieve proposed water quality targets in both the current and a range of potential future climates. However, there are important uncertainties about the effects of elevated atmospheric CO2 concentration on plant assimilation rates and the characterisation of extreme climate events that deserve further study.

159. Greenhouse gas mitigation potential from green harvested sugarcane scenarios in Sao Paulo State, Brazil

• Authors:
  • Adami, M.
  • Aguiar, D. A.
  • de Figueiredo, E. B.
  • Bordonal, R. de O.
  • Rudorff, B. F. T.
  • La Scala, N.
• Source: Biomass and Bioenergy
• Volume: 59
• Year: 2013
• Summary: Brazil is a major sugarcane producer and Sao Paulo State cultivates 5.5 million hectares, close to 50% of Brazil's sugarcane area. The rapid increase in production has brought into question the sustainability of biofuels, especially considering the greenhouse gas (GHG) emissions associated to the agricultural sector. Despite the significant progress towards the green harvest practices, 1.67 million hectares were still burned in Sao Paulo State during the 2011 harvest season. Here an emissions inventory for the life cycle of sugarcane agricultural production is estimated using IPCC methodologies, according to the agriculture survey data and remote sensing database. Our hypothesis is that 1.67 million hectares shall be converted from burned to green harvest scenarios up to years 2021 (rate 1), 2014 (rate 2) or 2029 (rate 3). Those conversions would represent a significant GHG mitigation, ranging from 50.5 to 70.9 megatons of carbon dioxide equivalent (Mt CO(2)eq) up to 2050, depending on the conversion rate and the green harvest systems adopted: conventional (scenario 51) or conservationist management (scenario S2). We show that a green harvest scenario where crop rotation and reduced soil tillage are practiced has a higher mitigation potential (70.9 Mt CO(2)eq), which is already practiced in some of the sugarcane areas. Here we support the decision to not just stop burning prior to harvest, but also to consider other better practices in sugarcane areas to have a more sustainable sugarcane based ethanol production in the most dense cultivated sugarcane region in Brazil. (C) 2013 Elsevier Ltd. All rights reserved.

160. Genotypic variability in the response to elevated CO2 of wheat lines differing in adaptive traits

• Authors:
  • Chapman, S. C.
  • James, A. T.
  • Dreccer, M. F.
  • Bourgault, M.
• Source: Functional Plant Biology
• Volume: 40
• Issue: 2
• Year: 2013
• Summary: Atmospheric CO2 levels have increased from similar to 280 ppm in the pre-industrial era to 391 ppm in 2012. High CO2 concentrations stimulate photosynthesis in C-3 plants such as wheat, but large variations have been reported in the literature in the response of yield and other traits to elevated CO2 (eCO(2)). Few studies have investigated genotypic variation within a species to address issues related to breeding for specific adaptation to eCO(2). The objective of this study was to determine the response to eCO(2) of 20 wheat lines which were chosen for their contrasting expression in tillering propensity, water soluble carbohydrate (WSC) accumulation in the stem, early vigour and transpiration efficiency. Experiments were performed in control environment chambers and in a glasshouse with CO2 levels controlled at either 420 ppm (local ambient) or 700 ppm (elevated). The results showed no indication of a differential response to eCO(2) for any of these lines and adaptive traits were expressed in a consistent manner in ambient and elevated CO2 environments. This implies that for these traits, breeders could expect consistent rankings in the future, assuming these results are validated under field conditions. Additional climate change impacts related to drought and high temperature are also expected to interact with these traits such that genotype rankings may differ from the unstressed condition.